GCSE Maths

Circles Question

Badz asked the following question:

"John runs twice round a circular pitch, which has a radius of 50 metres.
How far has he run? Give your answer in terms of pie [sic]."

Firstly, it's pi not pie, but that's an easy typo. Pi (normally written as the Greek letter π) is a very special number which goes on forever, but starts off: 3.141592... A pie is something the editor has eaten too many of, but that's another story!

The path around the outside of a circle is the circumference. The relationship between the radius and the circumference of a circle is this:

Length of circumference = 2 × radius × π

So once around the circular pitch in your question will be 2 × 50 × π = 100 × π

Since he goes around twice, the total distance run is 2 × 100 × π = 628 m.

Job done!

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